1. Field of Invention
The present invention relates to product delivery systems particularly suited for in gravitationally-fed sorters of transversely-spaced products moving along a direction of travel, which sorters separate transversely spaced products according to differences in their characteristics. In particular, the invention relates to a product flow control apparatus controlling the flow rate of products to be sorted, flowing at high rates induced by gravity which may be used in connection with relatively small, granular products to increase product density through the sorting machine and to increase sorting efficiency.
2. Description of the Related Art
A typical sorting machine of the type envisioned for application of the present invention is a gravity-fed high-speed sorting machine used for sorting small products, including fungible products in the food and pharmaceutical industries. For example, individual rice grains may be sorted to separate grains selected as “substandard.” In the art, “substandard” may apply to a grain having any undesirable characteristic, including color, shape, size or breakage, or any other characteristic not within the limits for acceptable products for a particular sorting. As used, product refers generally to the entirety of the item to be sorted, but may also be used to refer to an individual item.
Such a sorter incorporates a slide or chute at a steep angle having one or more channels across its width. A hopper or other feed system is positioned to dispense its product on the top of the slide. Gravity slide sorters have been in use for many years, sorting a wide variety of food products and many non-food products as well. Early sorters were single channel units, with a flat, “J,” “U”-, or “V”-shaped slide conveying product to a viewing area. Later, larger sorters were developed with 2, 6, 8, 12, etc., individual slides on a single frame. These individual slides were similar to the slides used on the single channel units, but economies were gained by constructing multiple slides on a single frame. These sorters presented multiple linear streams, or “strings”, of product to be viewed.
If multiple channels are used, the slide is divided across its width and configured so that an approximately evenly proportioned number of dispensed products are directed to each of the channels, Such techniques of distributing to each channel the proper amount of product being dispensed onto the slide are well-known in the art. A typical slide has numerous channels that may number as high as 64 or more, although slides for many machines in service today have only a limited number of channels, like 8, and in some applications it is preferable to use a single channel.
In the early 1980's, in response to the need for higher capacity sorters and to the need to sort products which would not flow smoothly down a slide, flat belt sorters were introduced. These sorters presented a wide sheet of product to the viewer.
In the mid-1980's a type of sorter was introduced which combined the simplicity and space efficiency of the discreet channel sorter with the high throughput capability of the belt sorter. These “broad slide” sorters presented multiple flat streams of product to the viewer. The total throughput of these multiple flat streams was often equal to the throughput of competing belt sorters.
Successful sorters have been developed for cereal grains using wide, flat slides, which present a “sheet” of product to the viewer/ejector system. The purpose of the slide is to accelerate and singulate the product, and to present it uniformly into the viewing area. This is similar to the product presentation of the belt sorter. Other successful sorters have been developed using slides that are also wide and flat, but in addition, have a series of dividing ribs separating the sheet of product into a series of “ribbons” of product, one per channel. These ribbons are presented to the viewer/ejector system oriented so that each ribbon passes in front of only one ejector. This important feature eliminates the condition of a defective product or article passing through the viewer in a location that causes two adjacent ejectors to fire at the same product, which often ejects an excessive amount of acceptable product along with the unacceptable. Logically, by eliminating the condition of product flowing through the zone of more than one ejector, a slide divided into channels, as just described, results in fewer total ejector fires and the removal of less good product.
Standard gravity-fed sorting machines, by virtue of requiring conveyance to the slide, require the product be transported laterally and cast onto the slide or guide. As a result, in the standard sorting machine the product may be impelled against a solid surface, in the case of a front conveyance system or enter the slide a low downward velocity on a path to contact the guide, in the case of a rear conveyance system. In operation, the gravity-fed products to be sorted are fed from a hopper, which feeds to the slide through a dividing vibratory feeder. The vibratory feeder is integrated within the sorting machine, but is sufficiently isolated to reduce vibration of the remainder of the sorting machine. Product then passes down the slide and before the viewer/ejector system, where each product is imaged, compared to sort criteria and then allowed to pass or deflected by the ejector system. Problematically, when first activated, the volume of products induced by the vibratory feeder to the slide, and therefore before the viewer/ejection system due to lack of uniform velocity and product singulation lacks a complete set of targets for sorting. Often machine users discard these initial sort results as lacking accuracy. Likewise, after the vibratory feeder ceases or when the product supply is exhausted, products to which the vibratory feeder has already imparted motion may be carried by momentum to the slide opening after vibratory feeder shutdown. Unacceptable products within this product group may not be sorted properly as a result of lack of uniform product velocity, alignment and singulation. In a typical sorting machine configuration unacceptable product in this additional amount may not be ejected from the product flow. The effect of this unacceptable flow is sometimes referred to as the “dribble effect.” As a result, unacceptable product, or contaminants, may be included in otherwise acceptable product. Finally, cessation of the vibratory feeder or exhaustion of the product supply may result in product being stranded intermediate the product supply and the slide, requiring the machine to be configured for operation to expel the unprocessed product, particularly if a different product is to be sorted.
Moreover, external vibrations may cause induce product flow, even in miniscule amounts, during times when the machine is not in operation, potentially contaminating sorted product.
Finally, the density of the product at the scan line, the point at which the sorting machine analyzes and determines whether any individual product is outside permissible parameters, drives the throughput of the sorting machine. Determination of whether the product is outside permissible parameters is accomplished by various optical equipment known in the art, such as cameras. Identification of an individual product outside of permissible parameters causes the sorter to cause an ejector to fire at the time the identified individual product will pass before the ejector. It is therefore advantageous to increase the density of the product passing through the sorting machine to the maximum density at which the optical equipment can image the passing product as this increases the throughput of the sorting machine, a desirable characteristic in the market as more product can therefore be processed.
The need therefore exists for a product control system which eliminates the lack of full through-put at start-up, eliminates the dribble effect, eliminates the potential for stranded material at shutdown, and eliminates potential contamination caused by external vibration, all while having no negative effect of through-put rate. It would be a further improvement if the product through-put were increased.